1. Field of the Invention
The present invention relates to a suitable chemical mechanical polishing apparatus and a chemical mechanical polishing method for polishing and planarizing the surface of a semiconductor wafer during the manufacturing process of a semiconductor device.
2. Description of the Related Art
Recent developments have produced high density integration of semiconductor devices and an accompanying pattern miniaturization, and in order to ensure the simple and reliable formation of particularly multi-layered miniature patterns, the planarization of the surface of a silicon wafer during the manufacturing process has become very important. Heretofore, a planarization method has been employed where a thick film of a material which is itself easily planarized is deposited on to the surface of the wafer to allow smoothing of any unevenness in the wafer surface. At this point chemical mechanical polishing methods are widely used as they allow the film on the wafer surface to then be polished to achieve even better planarization, and the film can also fill in any depressions which exist in the wafer surface.
Chemical mechanical polishing is a technique for planarizing the surface of a wafer whereby an alkali solution and a polishing slurry incorporating small abrasive particles are used to chemically and mechanically polish the wafer surface. An example of a conventional chemical mechanical polishing apparatus is shown in Japanese Patent Application, First Publication No. Hei-5-277908. FIG. 4 is a schematic diagram of the apparatus reported therein. As is shown in FIG. 4, a wafer carrier 1 which holds a semiconductor wafer W, and a polishing platen 3 on which is mounted a polishing pad 2 are positioned facing one another. Then, while the polishing pad 2, which is larger than the size of the wafer W, is rotated, the wafer W is pushed against the polishing pad 2 and rotated, and a polishing slurry which is supplied via a pipe 4 is then used to polish and thus planarize the surface of the wafer W.
However, because conventional chemical mechanical polishing apparatus employ large diameter polishing pads 2, the uniformity in the quality of the polishing pad can adversely effect the uniformity of the polishing. Furthermore, the apparatus is constructed so that the wafer W is polished by rotation against the large diameter polishing pad 2, and so a velocity differential develops between the central portion of the wafer and the outer portion of the wafer, due to a difference in the radius of gyration. Consequently, the outer portion of the wafer is polished to a greater degree than the inner portion, resulting in radial polishing irregularities on the wafer W.